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Synaptic error message -- how to respond

I have repeatedly received the following error message:
E: galternatives: package is in a very bad inconsistent state;
you should  reinstall it before attempting configuration

I don't recall what triggered it last week. Today I wanted to install "apt-rdepends" which displayed the above error message. I closed the message window. The box next to apt-rdepends was colored green indicating it had been successfully installed. I did a test run of it and got reasonably looking output.

I attempt to reinstall "galternatives" and receive:
E: /var/cache/apt/archives/galternatives_0.13.5+nmu4+deb9u1_all.deb:
subprocess new pre-removal script returned error exit status 1

What should I do next?